Process for preparing oximes



United States Patent 3,341,590 PROCESS FOR PREPARING OXIMES Lawrence R.Jones, Terre Haute, Ind., assignor to Commercial Solvents Corporation,New York, N.Y., a corporation of Maryland No Drawing. Filed July 6,1965, Ser. No. 469,929 8 Claims. (Cl. 260566) This invention relates toa process for the production of oximes. In a particular aspect thisinvention relates to a process for the production of oximes by treatmentof a secondary nitroparaflin with carbon monoxide in the presence ofsulfuric acid.

Oximes have a wide variety of uses. Cyclohexanone oxime is anintermediate in the production of caprolactam while methyl ethylketoxime and acetone oxime are used as anti-skinning agents in coatings.Many methods are known for producing oximes. One method involveshydrogenation of a nitroparaflin in the presence of sulfuric acid and ametal catalyst. Another method used for the production of cyclohexanoneoxime in particular involves the treatment of a water-soluble alkalimetal salt of nitrocyclohexane in the presence of sulfuric acid.

It is an object of the present invention to provide a process for theproduction of oximes.

Further objects and advantages of the present invention will be apparentfrom the specification and the appended claims.

The present invention resides in the discovery that oximes are obtainedby passing carbon monoxide into a sulfuric acid solution of a secondarynitroparaflin.

The nitroparaflins employed in the present invention are secondarynitroparafiins, that is to say nitroparafiins wherein the nitro group isattached to a carbon atom, which is in turn attached to two and not morethan two carbon atoms. Typically suitable nitroparafiins are representedby the formula RNO wherein R is a radical selected from the groupconsisting of cyclohexyl and and wherein R is a lower alkyl radical,that is an alkyl radical containing from one up to about three carbonatoms. Representative secondary nitroparafiins which may be employed inthe present invention include nitrocyclo hexane, 2-nitropropane,2-nitrobutane, 3-nitroheptane, etc., and the like. Oximes prepared fromsuch typically suitable nitroparafiins are represented by the formulaR=NOH wherein R is a radical selected from the group consisting ofcyclohexyl and wherein R is a lower alkyl radical. Representative oximesinclude methyl ethyl ketoxime, cyclohexanone oxime, acetone oxime, etc.,and the like.

The sulfuric acid solution of secondary nitroparaffin of use in thepresent invention may be prepared by any suitable means, as for example,by dissolving a secondary nitroparaffin in sulfuric acid. The sulfuricacid of the process may be of any suitable concentration even in excessof 100 percent, i.e. when excess S0 is present. When sulfuric acidsolutions of a concentration of less than 50 percent are utilized, thereaction proceeds slowly; whereas when the concentration of the acid isin excess of 100 percent, handling of the reaction mixture becomesdifiicult. As a compromise between the handling problems involved in theuse of sulfuric acid having a concentration of in excess of 100 percentand the slowness of the reaction when the sulfuric acid concentration isless than 3,341,590 Patented Sept. 12, 1967 50 percent, it is preferredthat the concentration of the sulfuric acid range from about 70 to about100 percent.

Themole ratio of'carbon monoxide to secondary nitroparaflin is ofimportance in the present invention. While oximes are obtained at lowerratios best results are obtained when the mole ratio of carbon monoxideto secondary nitroparafiin is in excess of 2: 1, for example 4-10: 1.While not deleterious to the reaction use of an additional excess ofcarbon monoxide serves no useful purpose.

The reaction is exothermic and requires no external source of heat. Thereaction takes place at temperatures as low as about 0 C. and as high asabout 100 C. At temperatures below 20 C. the reaction proceeds veryslowly While at temperatures above 60 C. the reaction proceeds sorapidly that it becomes difiicult to control. Therefore, temperatures offrom about 20 to about 60 C. are preferred in the present invention.

Oximes produced according to the process of the present invention may berecovered from the sulfuric acid reaction medium by any suitableprocedure. One such procedure involves neutralizing the reaction mediumwith a suitable base, then extracting the oxime from the neutralizedmedium with a suitable solvent for the oxime and finally removing thesolvent from the oxime.

The invention will be understood more fully by reference to thefollowing specific examples. It is understood that the examples arepresented for purposes of illustration only and are not intended as alimitation of the invention.

Example 1 Into a suitable reaction vessel containing 40 ml. of aqueoussulfuric acid (96% concentration) were slowly added 12.9 grams ofnitrocyclohexane. The resulting solution was cooled to approximately 20C. in a water bath and carbon monoxide was bubbled into the solution forone-half hour at a rate of approximately 1 to 2 pounds per hour. At theend of the one-half hour period, the resulting reaction mixture wasslowly combined with 200 mls. of distilled water and the pH of thecombination of water and reaction mixture was adjusted to 7.0 byaddition of sodium hydroxide. The resulting material was thenextracted-with ethyl ether. Cyclohexanone oxime was produced in a yieldof 34 percent based on the nitrocyclohexane starting material.

Example 2 Into a suitable reaction vessel containing 25 mls. of aqueoussulfuric acid percent concentration) were slowly added 12.9 grams ofnitrocyclohexane. The resulting solution was cooled in a water bath toapproximately 25 C. and carbon monoxide was bubbled into the solutionfor four hours at a rate of approximately 1 to 2 pounds per hour.Cyclohexanone oxime was produced in a yield of 52 percent based on thenitrocyclohexane.

The cyclohexanone oxime of Example 2 may be converted to caprolactam byconventional Beckmann rearrangement procedures. In one such procedurethe sulfuric acid reaction medium containing the cyclohexanone oxime isheated to from about to about C. for a period of approximately 1 to 2hours. If desired, the strength of the sulfuric acid may be increasedwith additional sulfuric acid or with S0 Example 3 A sulfuric acidsolution with carbon monoxide ple 2. Acetone oxime of 2-nitropropane istreated following the procedure of Examis obtained.

Example 4 Since many embodiments may be made of this invention and sincemany changes may be made in the embodiments described, the foregoing isto be interpreted as illustrative only and the invention is defined bythe claims appended hereto.

1 claim:

1. A process for the production of oximes which comprises providing asulfuric acid' solution of a nitroparafiin of the formula R-NO wherein Ris a radical selected from the group consisting of cyclohexyl and R(:JRH wherein R is a lower alkyl radical and passing carbon monoxide intothe said solution thereby producing oxirnes of the formula R=NOH whereinR is a radical selected from the group consisting of cyclohexyl andwherein R is a lower alkyl radical.

2. A process for the production of oximes which com- I prises providinga sulfuric acid solution of a nitroparaffin of the formula R-NO whereinR is a radical selected from the group consisting of cyclohexyl andwherein R is a lower alkyl radical the said solution having atemperature of from about 0 to about 100 C., passing carbon monoxideinto the said solution while maintaining the temperature of the saidsolution at from about 3 to about 100 C. thereby producing oximes of theformula R=NOH wherein R is a radical selected from the group consistingof cyclohexyl and wherein R is a lower alkyl radical.

3. The process of claim 2 wherein the temperature ranges from about 20to about C.

4. The process of claim 2 wherein the concentration of sulfuric acidranges from about to about percent.

5. The process of claim 2 .wherein the mole ratio of carbon monoxide tooxime is in the range of 2:1 to 10:1.

6. The process of claimv 2 wherein the nitroparaflin isnitrocyclohexane.

7. The process of claim 2 wherein the nitroparafiin is 2-nitropropane.

8. The process of claim 3 wherein the nitroparaflin is 2-nitrobutane.

References Cited UNITED STATES PATENTS 2,945,065 7/1960 Donaruma 260-566UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,341,590 September 12, 1967 Lawrence R. Jones pears in the abovenumbered pat- It is hereby certified that error ap atent should read asent requiring correction and that the said Letters P corrected below.

Column 4, line 4, for "about 3" read about 0 Signed and sealed this 31stday of December 1968.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer

1. A PROCESS FOR THE PRODUCTION OF OXIMES WHICH COMPRISES PROVIDING A SULFURIC ACID SOLUTION OF A NITROPARAFFIN OF THE FORMULA R-NO2 WHEREIN R IS A RADICL SELECTED FROM THE GROUP CONSISTING OF CYCLOHEXYL AND 